As a former county prosecutor and the first woman to be elected to the U.S. Senate from Missouri, Claire McCaskill has had to smash through many glass ceilings — in arguably the world’s biggest boys’ clubs.

While women are still far from earning equal pay to men (which was an issue the Democrat fought for during her time on Capitol Hill), they tend to undervalue or undermine themselves at work. And consequently, they end up leaving money on the table.

McCaskill, who is now an MSNBC political analyst and Know Your Value contributor, recently sat down with "Morning Joe" co-host Mika Brzezinski to discuss how women can stop sabotaging their own growth and success.

Here are some of the biggest self-inflicted wounds women make when it comes to money and negotiation at work:

Women want raises and promotions, but according to McCaskill, they don’t take the most crucial step: asking.

“The most important mistake that women make is not asking,” McCaskill said. “If you are not prepared to ask, then you are never going to get what you deserve. So, you’ve got to be willing to take risks and say to whoever you’ve gotta say it to: 'Hey, I’m worth more.'”

Brzezinski pointed out that men aren’t afraid to ask, sometimes more than once.

“Let me tell you what guys do,” she said. “They ask. They get a 'no', they go back. They ask as if they didn’t ask before, again, and yet we walk around thinking about it. We waste so much time and we leave so much money on the table.”

Women are pleasers and diplomats. This can be useful sometimes, but not at the negotiation table, according to McCaskill. She called it the “disease to please.”

“I think there’s this thing in the back of our heads too often that says ‘I don’t wanna rock the boat’,” said McCaskill. “‘I don’t want to be a problem employee. I don’t want be known as that woman.’”

McCaskill admitted she acted this way in the '90s when she was the only woman in the Jackson County, Missouri prosecutor’s office.

“I just thought I needed to lay low, because I thought, ‘I’m so lucky to be here, everybody else is a guy,’” McCaskill said. “In the long-run, I finally figured it out, but it took a while.”

McCaskill would go on to become the county’s first female prosecutor. She was later elected to state auditor before running for Senate in 2006. She won and held the seat until the 2018 midterm elections, when she lost to Republican opponent Josh Hawley by a small margin. She said her 12-year run in the Senate taught her a lot about rocking the boat.

Bosses are too busy to recognize your work all the time, so it’s important to speak up, McCaskill said. This is especially true if your goal is to get a raise.

“When you know that you’ve done a good job … then seek recognition,” she said. “And that doesn’t mean just employee of the month. That means making sure it’s on your evaluation, making sure that you assert yourself when it’s time for your evaluation that you’re expecting a raise.”

Unfortunately, women don’t usually “expect” a raise, she said. “Men expect a raise. Women see it as ‘Oh, I'm getting a raise!’”

Mom guilt can be a huge detriment during negotiations, according to Brzezinski, a mother of two daughters.

“We feel so guilty that we’re working and having kids,” she said. “Like, for some reason we’ve been given permission to be working 24 hours a day, and for some reason we feel guilty about that — and we bring it to our negotiation.”

McCaskill, a mom and grandmother, suffered a long battle with guilt when her kids were young.

“I did feel like especially in the public eye that people were going to be judging me as an inadequate mother if I was an adequate prosecutor,” she said. “You walk that tightrope, and you lose a lot of energy walking that tightrope.”